Reciprocating motor



Aug. 18, 1931. c. s. WEYANDT ET AL REC IPROCATING MOTOR Original FiledNov. 21, 1923 Patented Aug. 18, 1931 UNITED STATES PATENT cam. s.WEYANDT AND HAROLD E. FOX, or rimsnunon, rENus LvAmmnssIonons. BY MESNEASSIGNMENTS, 'ro CENTRAL ELECTRIC moor. COMPANY, a CORPORATION OFPENNSYLVANIA micrrnoca'rmo Moron. I

yon-ice Original application filed November 21, 1923, Serial No.676,106. Divided and this application filed May 5,

1928. Serial Our invention relates to magnetic circuit conductorsserving as casings for electric tools, and more particularly toiron-clad electromagnets.

In accordance with our invention, a metallic casing of magnetic materialhas a discontinuous periphery for electrically insulating the respectiveedges of said casing from each other.

Further in accordance with our invention the magnetic casing or housingis made of low carbon silicon steel and comprises a sheet of said steelrolled or bent into conduit-like form, the loose or free edges beingelectrically 5 insulated from each other by a thin layer of oxide.

Our invention further resides in apparatus of the character hereinafterdescribed and claimed.

In the accompanying drawings, Fig. 1 is a side elevational view of atube to be used as a casing; Figs. 2, 3 and 4 are end views of tubes ofdifferent shapes; and Fig. 5 is a longitudinal sectional view ofanelectric hammer of the reciprocating motor type, to which a casingembodying our invention may be particularly applied.

This application is a division of the subject;

matter in our Letters Patent No. 1,796,721,v granted March 26, 1929.

In constructing the magnetic housing constituting our invention we rolla sheet of low carbon silicon steel to substantially the desired shapeand size which is required to fit the electromagnet with which thecasing so formed is to be used. The loose or free side edges are thenloosely welded by the heat of the metal itself to form a rigid tubularstructure to permit machining or otherwise working on the tube. Afterthe tube is machined to proper length and other desired dimensions, theloose weld is broken open to rovide a slit in the casing to eliminatethe lnduced current losses that would be effected therein.

In preparing the tubes for service as casings, a sheet of silicon steelis rolled into a tube of substantially the desired shape and size asillustrated in Figs. 2, 3 and 4 and is cut to the approximate lengththat is desired. The sheet is preferably provided with tapered portions2 and 3 that will overlap somewhat when the tube is rolled. Theoverlapped portions arethen loosely welded. However such overlapping isnot essential, and theedges may simply abut each other as illustrated inFig. 3 of the drawings and then united by the non-permanent unionpreviously referred to.

."The surface of thelow carbon silicon steel has a thin layer of oxidethereon which pre-f fuse the two portions into a homogeneous vents afusing weld that would otherwise substance. Only a. surface. adherenceor loose weld is obtained. We employ the expression loose weld in thisapplication to comprehend a surface adherence, between two metals,

which may be easily broken b 'a relatively small force, as distinguishedrom a fusion Weld whereby the molecular structures of both metals areintimately mixed, or disposed, to, constitute a homogeneous mass.

The expression loose weld is intended to include lap welds, but-t weldsand any other Weld which is merely a surface adherence of i theaforementioned character. a

The loose weld so obtained between the overlappmg portions of the tubeis strong enough to maintain the tube as a rigidstruccorrosive-resisting material may be applied in any well knownmanner, though preferably by electroplating. g a

The metal which we preferably use for the magnetic housing or casingconsists of silicon steel having 2 to 4% silicon and low carbon content,preferably not exceeding 0.1%. Silicon steel of this character hashighelectrical resistance and high magnetic permeability and for a magneticcircuit is almost as good as laminated steel for reducing eddy currentlosses.

A tube of this metal is particularly applicable as a. casing for anelectromagnet. In Fig. 5 is illustrated an electric hammer of thereciprocating motor type to which we have applied the silicon steel tubeas a casing.

The hammer may comprise in general two operating coils 5 and 6. amovable piston or core 7, a barrel or guide 8 for the core 7, a tool 9that is struck by the core to do useful work, a shock-absorbing spring10 and a handle 11.

The coils 5 and 6 may be provided with magnetic circuits including endlaminations 13 and 14 and middle laminations 15. The laminations areprovided with pole tips 16 that extend into openings in the barrel 8 towithin a few thousandths of an inch from the inner surface thereof whichguides the movement of the core 7.

The. magnetic flux passing between the pole tips in the magnetic circuitof each coil acts upon the core to ell'ect its actuation in eachdirection.

In order to provide a protective casing that shall also serve as aconducting medium of low reluctance to the magnetic flux developed byboth coils, we provide casing 17 having low carbon content silicon steelwhich also has a high electrical resistivity and tends, therefore, todiminish eddy current losses. The peripheral discontinuity of the casingstill further diminishes eddy current losses by restricting the path ofsaid currents.

Casing 17 may have beveled ends, 17a, shown substantially as a 45 bevel,for effecting snug and close engagement of the casing with co-acting endpieces 18 and 19 when the same are forced towards each other. Themagnetic housing which forms a portion of the magnetic circuit orcircuits may therefore be positioned with respect to other sections ofthe magnetic circuit or circuits so that the reluctance therein due tojoints between said members may be substantially reduced.

Silicon steel has heretofore never been used in tubular form because ofthe difiiculty of effecting a solid or fusion weld. lVe have found.however, that a loose weld is sufficiently strong to permit machiningand thereafter, in an application, such as herein illustrated, as acasing for an iron-clad magnet, the opening of the weld introduces adesirable and serviceable air gap, for electrical resistance.

Although we have particularly specified silicon steel as the metal whichwe employ because of its desirable magnetic and electricalcharacteristics, it will be readily apparent that any other metal havingsimilar characteristics may be used. Moreover, the casing may be appliedto electromagnets of difierent types without departing from the scopeand spirit of the invention as set forth in the appended claims.

What we claim is:

1. In an electric motor, a reciprocatory magnetizable member, magneticoperating means associated therewith and comprising a winding andmagnetic pole elements energized thereby and spaced to form an air gap,and a tube-like casing for said motor of magnetizable material, theperiphery of said casing being discontinuous with the respect veperipheral edges electrically insulated w th respect to each other byoxide of the material of said casing.

2. In an electric tool, a reciprocating element of magnetizablematerial, and magnetizable structure associated therewith, saidstructure providing with said element a magnetic circuit and comprisinga longitudinallyslitted tube of low carbon steel containing from 2 to 4%silicon, and carbon not exceeding 0.1%.

3. The combination with an electric reciprocating motor, of a magneticcasing for said motor comprising a rolled sheet of magnetic metal, saidsheet having its edges substantially abutting and insulated from eachother by comparatively thin layers of oxide of said metal.

4:. The combination with an electric reciprocating motor, of a magneticcasing forming a part of the magnetic circuit of said motor comprising asheet of magnetic metal rolled into substantially cylindrical shape, theedges of said sheet substantially abutting each other and coated with acomparatively thin film of oxide of said metal to form an insulatingjoint longitudinally of said casing.

5. In an electric motor, means for producing a magnetic field, areciprocating element of magnetizable material, magnetizable structureassociated with said element and including a cylindrical member ofmagnetizable material having its circumferential continuity along itsentire length broken by a broken weld for preventing flow of currentstherein generated by the magnetic field of said motor, said memberproviding with said element a magnetic circuit for said field.

6. In an electric motor, means for producing a magnetic field, areciprocating element of magnetizable material, magnetizable structureassociated with said element and including a cylindrical member ofmagnetizable material having its circumferential continuity along itsentire length broken by a broken lap weld for preventing flow ofcurrents therein generated by the magnetic field of said motor, saidmember providing with said element a magnetic circuit for said field.

CARL S. WEYANDT. HAROLD E. FOX.

